Electrically heated tool



March 16, 1948. F, KUHN ET AL ELECTRICALLY HEATED TOCL Filed May 4, 1942 lrlll'vlIl-llll-l-Hn INVENTORS FRANK KUHN BY LAURENCE H.THOMAS A TTORNEYS 4 Patented Mar. 16, 1948 ELEOTRICALLY HEATED TOOL Frank Kuhn, Detroit, and Laurence H. Thomas, Birmingham, Mich, assignors to American Electrical Heater Company, Detroit, Mich, a

corporation of Michigan Application May 4, 1942, Serial No. 441,698

1 Claim. 1

The invention relates to electrically heated tools, such for instance as soldering irons.

It is one of the objects of the invention to ob tain a construction adapted for operation with electric currents of relatively low voltage. Thus for use on aircraft, the highest voltage available sometimes does not exceed twenty-four volts, and consequently constructions designed for use with commercial currents would not be suitable.

A further object of the invention is to obtain a construction which can be manufactured at low cost and which has various advantageous mechanical and electrical characteristics.

With these objects in view, the invention consists in a construction as hereinafter set forth.

In the drawings:

Figure l is an elevation of our improved tool, with the handle portion partly shown in section;

Figure 2 is an enlarged longitudinal section through the socket for receiving the tool the heating element associated therewith;

Figure 3 is a similar enlarged longitudinal section through the terminal connections;

Figure 4 is an elevation of a portion of Figure 3, viewed at right angles thereto;

Figure 5 is a perspective View of the insulator block in which the electrical terminals are se cured;

Figure 6 is a section substantially on line fi of Figure 3, illustrating the manner of locking the metallic socket to the insulator head; and

Figure 7 is an enlarged elevation showin the manner of attaching the heating resistor to the terminal contacts.

As illustrated in Figure 1, A is a soldering tool the shank portion of which is inserted in a socket B within a tubular housing 0 having a handle D at its rear end. The socket B is electrically heat ed and is of the following construction:

B is a metallic tube having integral therewith at its forward end an enlarged head B At its rear end is an insulator head E, preferably formed of a refractory material which, in addition to its insulating properties, is also heat resisting. A suitable material for this purpose is that which is commercially known as Lava. Surrounding the tubular portion B is an electrical heating unit formed by a helically wound resistor and an insulation therefor, preferably mica. As specifically shown in Figure 2, the refractory head E has a portion E extending within the end of the tubular portion B, a shoulder E which abuts against the end of the tube B, and a portion E of enlarged diameter which is flush with the outer surface of the tube B and extends rearward therefrom.

There is also an enlarged portion E in rear of the portion E F is a mica sheet wound around the outer surface of the tubular portion 38 and extending beyond the rear end thereof to overlap the portion E of the head E. The resistor G, preferably formed of a flat ribbon, is wound about the mica Fin the form of a helix. A second mica sheet F is then wound about this helix, and a return helix formed an extension of the resistor is wound about the sheet F. The opposite ends of the resistor pass through obliquely extending apertures E in the head E, from which point they extend through the casing C into the handle D to the terminal connections, which will be hereinafter described. In brief, the heating element comprises a resistor having two superimposed l c l portions with mice. insulation, surrounding the metallic tubular portion B. It will be noted that short-circuiting of the resistor through the metallic tube 13 is effectively prevented by ex tending the insulation F beyond the end of said tube to overlap the portion E on the head E. Thus, as the resistor is outside of the mica sheet F, it cannot come in contact with the metal tube.

The tubular casing C has its forward portion which surrounds the heating element slightly expanded in diameter, and the forward end of this portion engages the enlarged head B abutting against a shoulder B The rear end of the casing C extends within the handle D and engages a resilient clip H which centers it within the handle and also compensates for any change due to shrinkage or expansion. At the rear end of the casing C is an insulator block I of suitable moldable material such as Bakelite, which is of the following construction: The block I has a portion 1' which fits within the end of the tube C and with a shoulder I abutting against the end of said tube. The portion 1 has a pair of slots I extending longitudinally therethrough on opposite sides of the axis, and these slots communicate with open recesses or channels I on diametrically opposite sides of the block. Beyond this recessed portion is a central fin portion I having notches I in opposite edge portions thereof. The block I is inserted within the rear end of the handle D and supports the terminal connections for the resistor, which are of the following construction:

The end portions of the resistor, after passing out from the head E, are preferably reinforced by a metallic strip J wrapped thereabout, and these reinforced portions extend through an insulator tube K, preferably of porcelain, to a point adjacent to the block I. At their rear ends the reinforced portions of the resistor are connected to terminal bars L and L, preferably by spot welding. These bars are adapted to be inserted through the slots I into the open channels I and are there connected to the flexible conductors in the following manner: M is the flexible conductor cord containing the insulated strands M and M which latter are passed on opposite sides of the fin I and oppositely through the notches 1 They then extend forward into the channels I and the conductor wire is attached to the bars L and L' by screws N and N. These screws engage threaded apertures in said bars and are of suficient length to enter into recesses I which serve as a locking means preventing the withdrawal of the bars from the block I. They also in connection with the notched fin I form an anchorage for the flexible conductor cord M, preventing the accidental disengagement thereof.

The elements of our improved electrically heated tool, as above described, are assembled as follows: The head E is first attached to the rear end of the socket B by cementing the portion E into the end of the tubular portion 13'. A sheet of mica insulation is then wrapped around the tubular portion B and the portion E of the head which is flush therewith. The resistor G is then passed through one of the apertures E in the head E and wound helically about the mica insulator F to the upper end portion of the tube B. A second mica sheet F is then wrapped about the helix, and the resistor is wound thereabout helically in a downward direction, then passing through the second aperture E in the head E. The opposite end portions of the resistor which have been reinforced by the metallic strip J, as previously described, are then passed through separate channels in the porcelain tube K to pro- ,iect out from the lower end thereof. The pro- ,iecting end portions are then spot welded to the bars L and L, as previously described. The outer casing or tube C is then sleeved over the socket B and the insulated resistor thereon, the upper end of said tube engaging the portion B ofthe socket and abutting against the shoulder B The block I is next engaged with the bars L and L and the portion I of said block is inserted in the rear end of the tube C with the end of said tube abutting against the shoulder 1 A portion of the tube is then bent inward to engage a notch I in the portion 1', thereby locking the block from disengagement from the tube C.

The flexible conductor M is next attached to the block I, as previously described, after which the casing C and block I are inserted within the handle D and resilient clip H. When thus assembled, all of the elements of the tool are secured from displacement.

While we have specifically described our improved electrically heated tool as a soldering iron, it is obvious that it is adapted for other uses.

What we claim as our invention is:

A terminal connection for an electrical heating resistor comprising a longitudinally extending metallic strip wrapping for the end portion of the resistor, a'bar of greater thickness and cross section welded to the outer end portion of said wrapping, and a binding screw threadedly engaging said bar and adapted to secure a service conductor thereto.

FRANK KUHN. LAURENCE H. THOMAS.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 897,674 Swan Sept. 1, 1908 979,904 Wooge Dec. 27, 1910 1,027,337 Holmes May 21, 1912 1,127,280 Read Feb. 2, 1915 1,154,415 Kuhn et a1 Sept. 21, 1915 1,270,303 Kuhn et a1 June 25, 1918 1,388,373 Richtmyer Aug. 23, 1921 1,693,899 Horle Dec. 4, 1928 1,810,164 Fay et a1 June 16, 1931 1,819,554 Hanson Aug. 18, 1931 1,824,447 Richter Sept. 22, 1931 1,95 ,426 Ellinger Mar. 27, 1934 1,961,496 Holmes June 5, 1934 1,975,623 Siegel Oct. 2, 1934 2,003,625 Boyer June 4, 1935 2,041,018 Persons May 19, 1936 2,064,645 Abbott Dec. 15, 1936 2,177,509 Abbott Oct. 24, 1938 2,258,252 Lang Oct. '1, 1941 FOREIGN PATENTS Number Country Date 800,316 France Apr. 27, 1986 

